I am wondering if it is too late in the season to divide hostas. Would it be better to wait until spring and, if so, how early should I do it. Thanks, Lesley
The conventional wisdom on hosta division is to divide every three years or so. However, if you have chosen your initial site wisely, and provided adequate care at planting time, and proper subsequent maintenance, hostas can remain in place without division for many years, growing to their full potential (which is often much larger than people expect: pay attention to the dimensions on the plant tags and add up to 6-12 inches/15-30 cm, or more). They only require division if the middle of the plant is starting to die out. I have had a hosta remain in place in the ground for 15+ years without significant division; others have been thriving in pots for about 5+ years.
Hostas, like many other perennials, are best divided in spring (when new growth appears) or in fall (when the plant starts to go dormant). Please note: our Garden Guides are currently under extensive updating. Please be patient with us, and refer to the Guide in the future.
In order to thin your plants, a good approach might be to first water the plants thoroughly a couple of days before. Do this on a sunny day when rain is not expected, and early in the day – to deter slugs and snails. Prepare your planting holes or pots for the divisions ahead of time, mixing some compost either into your garden soil or into potting soil in pots. Water the soil or pots deeply.
Early in the day of division, plunge a flat-bladed spade into a section of the crown, and separate out a portion of the plant. This allows the main plant to continue to thrive; it may be a little odd-shaped the following year (i.e. not completely circular) but this would be disguised by the close neighbouring hostas in your bed, and the plant likely will resume its circular shape within a couple of growing seasons. Make sure to get a decent-sized section of plant that includes several “eyes”. See the below link for dividing and potting up hosta divisions. You should probably trim some of the roots (to encourage feeder roots to develop) and cut off all but one or two of the youngest leaves (this allows the plant to continue to manufacture food through the remaining leaves, but reduces moisture evaporation through foliage). Do not fertilize the divisions, and keep them in full shade (moist but not soggy) until they start to show good regrowth with a number of new leaves. They can then be repotted or transplanted into the garden.
NH hostas, linked below has a video to assist you.
Happy gardening: good luck with your hosta division anytime now, the fall.
Sidenote 1: Instead of discarding your hosta divisions, you may want to put them out on the sidewalk (even in plastic bags if you don’t have pots). You may find that people in your neighbourhood appreciate free plants. :)